I Just upgraded to A 75 gallon tank, from A 25 gallon. I had to do this rather quick do to the fact that 25 cracked. So I will give a quick update. I added all new live sand to the 75gallon Carib Sea.( Did not transfer any of old Substrate over) I only have about 50 ILBs of live rock in the 75. Bye the way I added 80 ILbs of the Carib Sea live sand. For flow I have added two Korella 1080, they are placed at upper corners of tank. so I can get some surface breakage. I also have Reef octopus BH 1000 HOB skimmer. I recently added A penguin bio wheel to remove remaining debris, also so I can run carbon. Now after the update to get to my question. I can not keep My Alk level up. It stays around 7 DKH using API test kit. I am supplementing with the Bulk Reef supply Soda Ash also dosing the calcium solution as well I test its At seven It takes about 100 ml to bring to eight, I do this around 4:00 pm then at about 10:30 I will add another 100ml but also dose about 100ml of calcium additive with it. Mag was low and now at 1350 and holding calcium also at 450ppm. Calcium has remained at 450 through all this. Take that back was at about 500ppm but for two days just dosed alk. then came to 450 and sine dosing equally at 10:30 remained at 450ppm Alk is only issue. Sorry for being so long just trying to give as mutch info as possable. All corals along with fish Are doing OK. Corals are not perfect but think there adapting to new light went from A 4x24 T5 to the marine land pro with 4x54watt T5 and duel 150 HQI